Distillation unit



May 25,l 1937. J. s. WALLIS ET AL DISTILLATION UNIT Filed Nov. 4, '1951 ../@ww *j Q www .1/ n Tr mw. 6 1/ 4/ 0 d @/MM/ y@ mw ///V/ /V/ i MM5 E .f MM A 1.., ../,f//f/ w m/ MM w v/ l@ m5 M mf dnl-l l Patented May 25, 1

.lohn S. Wallis and .lohn C. Mahoney, New York, to Alco Products, Incorporated,

New York, N. Y., a corporation S T A E .L

DISTILLATION UNIT N. Y., assignors of Delaware Application November 4, 1931, Serial No. 572,890

Our invention relates to nace construction and more 4 Claims.

a tube still and ful'- particularly to a two stage distillation unit for use in p-rocessing and pyrolytic treatment of petroleum hydrocarbons.

Of late in the distillation of petroleum oils, for the recovery of certain products, particularly lubricating oils, it has been duct the distillation in two the practice to constages consisting of an atmospheric stage and a sub-atmospheric or vacuum stage. In a distilla tion unit for practicing such a process, two furnaces are always emthe cost separate ployed. Obviously naces with their pensive. pressure, the oil is usually 375 of building two furfoundations, is ex- In the distillation under atmospheric preheated to about F. When the oil enters at this temperature, it has been found that the flue gas temperature is usually in enters between 500 and 600 perature falling between 700 is manifest that this high the neighborhood of 570 F. The oil entering the vacuum distillation unit between 500 F. and

been found that the flue gases still, where the oil F. are at a tem- F. and 800 F. It flue gas temperature existing in connection with the vacuum stage makes for a low thermal efficiency.

One object of our inven two stage distillation unit tion is to provide a in which both the atmospheric and the vacuum stages are incorporated in a single unitary structure.

Another object of our invention is to provide a furnace construction for the practice of a two stage distillation process 1n which greater thermal efficiency is obtained.

A further object of our invention is to provide a furnace embodying both vacuum distillationstages in expense entailed in the con arate furnaces.

Other objects the atmospheric and order to reduce the struction of two sepwill appear from the detailed description of our invention appearing below.

Figure 1 shows a sectional elevation of a two stage unit embodying our invention.

Figure 2 is a schematic diagram showing the flow of distillants through a still unit embodying our invention.

In general, our invention contemplates a tube still embodying a furnace construction having a casing and a bridge wall forming ent combustion chambers.

two independ- Independent means are provided for introducing fuel into the respective combustion chambers.

bustion chamber is a bank be heated mainly by the ra Over one cornof tubes designed to diant heat generated in one combustion chamber. Over the other combustion chamber is a second bank of tubes adapted to be heated mainly by the radiant heat there developed. A second bridge wall is positioned close to one end of the casing forming a passage through which the exhaust gases of both combustion chambers flow. Positioned within this passage are two banks of convection tubes. These banks are connected to their respective radiant banks as shown in the flow diagram in Figure 2.

More particularly referring now to the drawing, Figure l, shows a longitudinal section of a unit embodying our invention having two combustion chambers l and 2, separated by a bridge wall 8. Oil burners 3 and 4 are arranged to burn oil in the respective combustion chambers. It is to be understood that, while we have shown an oil fuel red unit, pulverized or other fuels may be used without departing fro-m the scope of our invention. The radiation heated bank 5 of the atmospheric stage is positioned above the combustion chamber l. It is to be noted that all the tubes in the atmospheric stage radiation bank are of the same size. This radiation bank will be referred to hereinafter as the atmospheric radiation bank. Over the chamber 2 is positioned a bank of tubes 6 adapted to be heated mainly by the radiant heat developed in the lcombustion chamber 2. Inasmuch as this bank is subjected to a reduced or sub-atmospheric pressure, this bank will be hereinafter referred to as the vacuum radiation bank. It is to be noted that the upper tubes l2 are of a larger size than the lower` tubes i3. The object of this arrangement is to permit the vacuum or reduced pressure at the outlet end of this bank to travel back through the tubes. This is described in United States patent to Harnsberger, 1,666,597.

A second bridge wall 9 protects the convection banks l0 and 1 from the radiant heat developed in combustion chamber 2. This bridge wall 9 in connection with the rear wall of the furnace forms a passage through which the products of combustion flow downwardly as indicated by the arrows, and out through flue connection ll into the smoke stack. In this passage are positioned two sets of convection heated tubes. The upper tube bank i0, as will be seen from the flow diagram in Figure 2 is connected in series with the vacuum radiation bank. The lower convection bank l, as is shown in the flow diagram in Figure 2 is connected in series with the atmospheric radiation bank. The arrows in Figure 1 indicate the path of the products of combustion through our unit. The ow of the liquid to be distilled is shown in Figure 2 Where the incoming oil, after being preheated, enters the atmospheric convection heated bank, passes through the atmospheric radiation heated bank from the outlet of which the heated products are directed to an evaporating or separating stage, wherein a division of the products is made, certain fractions of which are returned to be processed by the vacuum stage of the unit. In the vacuum stage, the distillant enters the convection bank, flows rst through the tubes of smaller diameter in the vacuum radiation bank, then through the tubes of larger diameter in the vacuum radiation bank to the vacuum outlet, thence through Vacuum distilling and condensing equipment, not shown.

In normal operation the combustion chamber I will be so fired by burners 3 as to'maintain a temperature at the upper end of the bridge wall 8 of 1300o F. The combustion chamber 2 will be red by burners 4 to maintain a temperature at the upper end of the bridge wall 9 of about 1300o F. The products of combustion from both combustion chambers will leave the unit at an outlet temperature which is determined by the inlet temperature normally used at the inlet of the atmospheric stage.

By varying the iiring rate of the respective burners 3 and 4, it is manifest that a large variation and consequent flexibility can be obtained in the thermal input between the atmospheric radiation bank and the vacuum radiation bank. For example, if the combustion chamber i is red to 1300 F. at bridge wall 8, the burners 4 will be red very lightly and thus give very little heat absorption in the vacuum radiation bank 6. Conversely, burners 3 may be fired very lightly in order to give a bridge Wall temperature at bridge wall 8 of 1000 F. or less. In this case, it would follow that burners 4 may be red to their limits, namely about 1300" F. over the bridge wall 9. It is to be noted that a temperature of 1400o F. at the top of bridge Wall 9 where the products of combustion enter the convection bank, should not be exceeded in order to prevent a decomposition of the petroleum oil with a consequent deposit of carbon. By this regulation of the firing rates, the heat absorption between atmospheric radiation bank 5 and vacuum radiation bank 6 can be controlled through an exceedingly wide range. Inasmuch as about 70% to 80% of the entire work is accomplished in the radiant tube banks, the degree of flexibility will be well within the range of normal operations.

It will be seen that our construction gives a very compact and efcient unit. A high degree of flexibility is obtained, together with a high thermal efciency, giving an optimum result for use in processing of petroleum hydrocarbons. It is clear that our invention is applicable to units of varying sizes and that it is particularly useful in connection with smaller units where the saving of expense in construction is correspondingly greater. It will be seen that we have provided a novel and eilicient construction which accomplishes the object of our invention.

It will be understood that certain features, and sub-combinations are of utility and may be emi ployed without reference to other features and sub-combinations. is within the scope This is contemplated by and of the appended claims. It

is further obvious that various changes may be made in details within the scope of the claims appearing hereinbelow, Without departing from the spirit of our invention and it is, therefore, to be understood that our invention is not to be limited to the specic details shown and described.

Having thus described our invention, what we claim is:

1. In a two stage distillation unit, the combination including; a casing, a bridge Wall within said casing forming two combustion chambers, independent means for burning fuel in the respective combustion chambers, a radiation tube bank located over one combustion chamber, a radiation tube bank located over the second combustion chamber, a second bridge wall, two convection tube banks disposed between said second bridge wall and said casing, one of said convection tube banks being connected in series with one of said radiation tube banks and the other ection tube banks connected in series with the other of said radiation tube banks.

2. A two stage distillation unit comprising in combination; a casing, a bridge wall forming two combustion chambers, supplying heat to said combustion chambers, a horizontally disposed atmospheric radiation tube bank in one combustion chamber, a horizontally disposed Vacuum radiation tube bank in the other combustion chamber, a second bridge wall forming an exhaust passage for the products of conibustion from both said combustion chambers, two vertically disposed convection tube banks located in said passage, one of said convection tube banks connected in series with said atmospheric radiation banks, thc other of said convection tube banks connected in series with said vacuum radiation tube banks, and separate inlets and outlets for said atmospheric and vacuum stages.

3. A furnace construction for processing hydrocarbon oils comprising in combination a setting, a bridge wall dividing said setting into two sections, independent means for burning fuel disposed in each of said sections, respective tube banks disposed in each of said sections to be heated mainly by radiant heat, a common passageway for gases from said respective sections, separate tube banks to be heated mainly by convection heat disposed successively along and within said common passageway, each of said convection heated banks being connected to a respective one of said radiant heated banks and means for separately charging a stream of oil to each convection bank.

4. A furnace construction for processing hydrocarbon oils comprising in combination, a setting, a bridge wall dividing said setting into two sections, independent means for burning fuel disposed in each of said sections, respective tube banks disposed in each of said sections to be heated mainly by radiant heat, a common passageway for gases from said respective sections, separate tube banks to be heated mainly by convection heat of said gases disposed successively along and within said common passageway, said passageway being formed in part by a wall common to it and one of said sections, each of said convection heated banks being connected to a respective one of said radiant heated banks and means for separately charging a stream of oil to each convection bank.

JOHN S. WALLIS. JOHN C. MAHONEY.

of said conindependent means for 

